Lecture 12 - Lungs & Mediastinum Flashcards
What is the mediastinum?
- central compartnement of th thoracic cavity
(recall that other components of the thoracic cavity are the right and left pleural cavities and the pericardial cavity)
what borders the mediastinum laterally?
lungs and pleural cavities
What does themediastinum contain?
thoracic viscera outside of the lungs
Where do the superior and inferior mediastinum divide?
Where the manubrium and sternal body meet
What are the two divisons of the mediastinum?
- superior mediastinum
- inferior mediastinum
Superior mediastinum: viscera
- superior portions of the esophagus and trachea
Superior mediastinum: vessels
- arch of aorta and branches
- superior vena cava and brachiocephalic veins
Inferior mediastinum divisons (3)
- anterior
- middle
- posterior
Inferior mediastinum- anterior
- between the sternum and heart (pericardium)
- contains the thymus gland
Inferior mediastinum - middle
- contains the heart and roots of the great vessels
Inferior mediastinum - posterior
- betweent he heart (pericardium) and vertebral column
- contains the thoracic aorta, inferior esophagus, azygous system
Thymus gland
- lymphoid organ
- important site of white blood cell (T cell) maturation; hormone production
openings of the diaphragm
- inferior vena cava
- esophagus
- aorta
Conducting portion vs respirstory portion
conducting portion of lungs (passage of air) structures (9)
- nasal cavity
- pharynx
- larynx
- trachea
- primary bronchi
- secondaey bronchi
- tertiary bronchi
- bronchioles
- terminal bronchioles
Where does he trachea bifurcate?
the carina
What does the trachea bifurcate into? (2)
- left primary bronchi
- right primary bronchi
what muscle is on the posterior side of the trachea?
the trachealis muscle
what surrounds the trachea?
c-shaped cartilage rings
what do the primary bronchi turn into?
secondary/lobar bronchi
how many lobar bronchi does the right side have? How many does the left side have?
- right = 3
- left = 2
What do the secondary/lobar bronchi turn into?
tertiary/segmental bronchi
How many tertiary/segmental bronchi do we have in each lung?
9-10 in each lung
what do the tertiary/segmental bronchi do?
each supplies a bronchopulmonary segment
Each lung has an apex (top) and base. What does the left lung have that the right lung does not?
cardiac notch (the heart is on the left side)
Gross anatomy of the right lung
- superior lob
- horizontal fissure
- middel lobe
- oblique fissure
- inferior lobe
Gross anatomy of the left lung
- superior lobe
- cardiac notch
- oblique fissure
- inferior lobe
what do the hilum cotains? (3)
- pulmonary artery
- pulmonary vein
- bronchus
Lung hilum
both right and left lung has a hila
pleural membranes
- parietal pleura (superior to parietal pleura)
- visceral pleura (superior to lungs, deep to parietal pleura)
Parietal pleura
covers the inner surface of the thoracic wall and extends over diaphragm and mediastinum
Visceral pleura
covers the outer surfaces of the lungs; extends into th fissures between lobes
Pleural cavity/space
- potential space between the visceral and parietal pleura
- contains a small amount of pleural fluid (lubricates pleural surface to reduce friction during lung inflation and deflation)
respiratoy portion of lungs (3)
- respiratory bronchioles
- alveolar ducts
- alveoli & alveolar sacs
alveoli & alveolar sacs
- each alveolar duct ends in an expanded region known as alveolar sac
- alveolar sacs aer made up of cluster of alveoli (main site of gas exchange)
How many alveoli does each lung have?
approximately 150 million
Alveoli
- primary site of gas exchange (O2 into bloodstream, CO2 out of bloodstream)
- extensive capillary network surrounds each aveolus
- elastic fibers surround alveoli which facilitate stretch & recoil during gas exchange
plmonary arteries function
carry deoxygenated blood from the rigth ventricle of the heart to the lungs
pulmonary veins function
carry oxygenated blood from the lungs to the heart (left atrium)
Where do the pulmonary arteries and vens enter and exit the lungs via…?
the respective hilum
branches of the pulmonary arteries & veins surround the alveoli of the lungs to…
facilitate gas exchange
what nerves innervate the diaphragm?
left and right phrenic nerves
Bronchial arteries
carry oxygenated blood to the lungs and bronchi and drain into the azygous system
Autonomic innervation of the lungs
- sympathetic innervation: bronchodilation
- parasympathetic innervation: bronchoconstriction
Pressure and volume
inversely related
mechanisms of breathing: inspiration -secondary muscles
- external intercostal muscles (elevate ribs)
mechanisms of breathing: inspiration - primary muscle
- diaphragm (contracts and flattens)
Pressure and volume: inspiration
- as lung volume increases, pressure in lungs decreases relative to atmopheric pressure
- air is drawn into the lungs
Pressure and volume: expiration
- as lung volume decreases, pressure in the lungs increases relative toatmospheric pressure
- air flows out of the lungs
mechanisms of breathing - inspiration
- expansion of the chest cavity in 3 dimensions
- decreased pressure pulls air into the lungs
mechanisms of breathing - expiration
elastic recoil of the alveoli
- decreases thoracic & lung volume
- increased pressure expels air from the lungs
mechanisms of breathing: expiration - primary muscle
- diaphragm (relaxes, structures return to pre-inspiration position)
Q
mechanisms of breathing: expiration -secondary muscles
- internal intercostal muscles (depress ribs)
Exchange of O2 and CO2 between lungs and blood takes place by ____ across the _____ and _____ ____
- diffusion
- avleolar
- capillary walls
O2 and CO2 move between alveolar air and blood via a _____ _____
diffusion gradiant
O2 enters the _______ ______
respiratory portion (inspiration)
O2 diffuses from the _____ across the _______ _______ into the _________, where it can bind to the ____ and trasnported around the ______
- alveolus
- repiratory membrane
- capillary
- RBCs
- body
CO2 is expelled via ___
expiration
CO2 diffuses acrss the repiratory membrane into the ____
alveolus
